In accordance with legal regulations, all freight and mailing shipments that are to be transported by an aircraft are to be subjected, before loading, to a freight scanning, in order to rule out manipulations and, in particular, to prevent freight that contains an explosive charge from being introduced into an aircraft. The inspection of large freight and package quantities by ground personnel, however, is expensive and time-consuming and, moreover, dangerous. Therefore, so-called simulation chambers or explosion or detonation chambers are used, in which large freight, airmail, and package quantities can be examined for explosive charges, whose igniters respond to barometric, acoustic, or electromagnetic signals. Such a simulation chamber is, for example, known from DE 4115713 C1. The freight to be inspected is introduced for this purpose into a closed explosion chamber. Real-time conditions are specified in the explosion chamber, which coincide with the actual ambient conditions or the ambient conditions to be expected on the intended flight path. If a detonable explosive charge whose igniter responds to the conditions simulated in the explosion chamber is found in the explosion chamber, it is, as a rule, thereby destroyed. However, in this way, it can be prevented that the freight containing the explosive charge is introduced into the aircraft and is detonated during the flight or upon landing.
The known simulation chambers can detect explosive charges contained in freight whose igniters respond to barometric signals (excess or reduced pressure), acoustic signals (such as sound waves in the frequency range of 1-20 kHz, which are above a detectable acoustic pressure), or electromagnetic signals (such as radio signals in the frequency range between 120 kHz and 1 GHz).
Recently, freight packages have appeared that are provided with explosive charges that cannot be detected by the known simulation chambers nor by other known air freight testing methods (such as by X-ray investigation or by the detection of traces of explosive materials).